Deadwood Reservoir
Valley County, Idaho3,800 acresView mapDirections
Idaho DEQ publishes the water-quality measurements for Deadwood Reservoir. Here is what has been measured.
- Oligotrophic
- Limited data
Deadwood Reservoir in Valley County, Idaho has water-quality measurements published by Idaho DEQ, shown here as reported. Water clarity: 17.2 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 1.7 µg/L. Surface area: 3800 acres.
Deadwood Reservoir is a 3,800-acre cold, clear oligotrophic lake in Valley County, Idaho. Water clarity is declining over recent sampling years. Compared to the 8 other monitored lakes in Valley County, Deadwood Reservoir ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, IDEQ, last sampled 2021-08-04. Methodology: how these readings are compared.
Deadwood Reservoir covers about 3,800 acres in Valley County. For a place on the water, look through cabin and lake-house rentals near Deadwood Reservoir on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Deadwood Reservoir is good for
From access and monitoring records, not editorial picks.
- Clear water17.2 ft of visibility
- Big water3,800 acres
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Deadwood Reservoir is safe to swim in today is a call for the Idaho Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Deadwood Reservoir
These are the measurements Idaho DEQ publishes for Deadwood Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 17.2 ft down. Phosphorus 14 µg/L. Chlorophyll-a 1.7 µg/L. TSI 38.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 17.2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 14µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 1.7µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 38 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Deadwood Reservoir
Answers come straight from the public measurements and survey records on this page.
→ Deadwood Reservoir water level: the live USGS gauge reading
Lake Details
Surface area
3,800 acres
No bathymetric survey has been published for Deadwood Reservoir, so its depth is not documented here.
Stays via Stay22
Stays near Deadwood Reservoir
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Top-rated places to stay near Deadwood Reservoir
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Fishing Deadwood Reservoir
Water Quality Trend: Stable
Based on 6 years of monitoring (2012–2021).
Water clarity
Worsening6 years
Phosphorus
Stable-0.08 µg/L/yr3 years
Chlorophyll-a
Improving-0.09 µg/L/yr6 years
Reservoir Info (USACE NID)
Deadwood Reservoir is a man-made reservoir impounded by the Deadwood Dam (completed 1931), built primarily for hydroelectric on the Deadwood River South Fork Payette River; concrete-type dam, 165 ft tall and 749 ft long.
- Surface area
- 3,800 ac
- Max storage
- 153,992 ac-ft
- Drainage area
- 109.43 sq mi
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
All listed purposes: Hydroelectric;Irrigation;Recreation.
Source: USACE National Inventory of Dams, NID ID ID00284 · Operator website
Nearby Lakes in Valley County
Frequently asked questions about Deadwood Reservoir
Where is Deadwood Reservoir?
- Deadwood Reservoir is a lake in Valley County, Idaho. Its water-quality measurements are published by Idaho DEQ and shown on this page as reported.
What is the water quality of Deadwood Reservoir?
- Deadwood Reservoir in Valley County, Idaho has water-quality measurements published by Idaho DEQ, shown here as reported. Water clarity: 17.2 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 1.7 µg/L. Surface area: 3800 acres.
Is Deadwood Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Explore Deadwood Reservoir across LakeQuality
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Species activity outlook by water temperature and season
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Where this data comes from
15 measurements from 1 monitoring station, 2012–2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Bureau of Reclamation
1119USBR_WQX15 samples · 2012–2021
Analytical methods
- Depth, Secchi disk depth
- Zebra/Quagga Mussel APHA 10200G Modified
- Phosphorus by Single Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.